A session border controller (SBC) assists in the connecting, conducting and disconnecting of media streams. In addition to multi-media services, such as VoIP and video conferencing, SBCs may provide other functions, such as security or traffic management. SBCs may implement session initiation protocol (SIP) for creating, modifying, and terminating sessions, which may include one or more media streams. SIP involves the selection of addresses and ports used by the source and destination of the media stream.
SBCs may be employed at the border between two networks to implement network policies. The network policies dictate the particular addresses and ports used for media in a VoIP session. In other words, SBCs are statically configured to provide specific addresses and ports in VoIP without regard to the actual reachability of the endpoints of the session. Problems may arise when the network policies do not match the actual reachability of the endpoints.